New discovery at Tel Aviv University excavation of Qesem Cave reveals tortoises played a supplementary role in the diets of early humans 400,000 years ago

Grilled, boiled or salted? Turtles, or tortoises, are rarely consumed today, but a select few cultures, primarily those in East Asia, still consider turtle soup, made from the flesh of the turtle, a delicacy.

According to a new discovery at Qesem Cave near Tel Aviv, the site of many major findings from the late Lower Paleolithic period, they are not alone in their penchant for tortoise. Tel Aviv University researchers, in collaboration with scholars from Spain and Germany, have uncovered evidence of turtle specimens at the 400,000-year-old site, indicating that early man enjoyed eating turtles in addition to large game and vegetal material. The research provides direct evidence of the relatively broad diet of early Paleolithic people — and of the “modern” tools and skills employed to prepare it.

The study was led by Dr. Ruth Blasco of the Centro Nacional de Investigacion Sobre la Evolucion Humana (CENIEH), Spain, and TAU’s Institute of Archaeology, together with Prof. Ran Barkai and Prof. Avi Gopher of TAU’s Department of Archaeology and Ancient Near Eastern Civilizations. Other collaborators include: Dr. Jordi Rosell and Dr. Pablo Sanudo of Universitat Rovira i Virgili (URV) and Institut Català de Paleoecologia Humana i Evolució Social (IPHES), Spain; and Dr. Krister T. Smith and Dr. Lutz Christian Maul of the Senckenberg Research Institute and Natural History Museum, Germany. The research was published on February 1, 2016, in Quaternary Science Reviews.

“Culinary and cultural depth” to the Paleolithic diet

“Until now, it was believed that Paleolithic humans hunted and ate mostly large game and vegetal material,” said Prof. Barkai. “Our discovery adds a really rich human dimension — a culinary and therefore cultural depth to what we already know about these people.”

The research team discovered tortoise specimens strewn all over the cave at different levels, indicating that they were consumed over the entire course of the early human 200,000-year inhabitation. Once exhumed, the bones revealed striking marks that reflected the methods the early humans used to process and eat the turtles.

“We know by the dental evidence we discovered earlier that the Qesem inhabitants ate vegetal food,” said Prof. Barkai. “Now we can say they also ate tortoises, which were collected, butchered and roasted, even though they don’t provide as many calories as fallow deer, for example.”

According to the study, Qesem inhabitants hunted mainly medium and large game such as wild horses, fallow deer and cattle. This diet provided large quantities of fat and meat, which supplied the calories necessary for human survival. Until recently, it was believed that only the later Homo sapiens enjoyed a broad diet of vegetables and large and small animals. But evidence found at the cave of the exploitation of small animals over time, this discovery included, suggests otherwise.

Open questions remain

“In some cases in history, we know that slow-moving animals like tortoises were used as a ‘preserved’ or ‘canned’ food,” said Dr. Blasco. “Maybe the inhabitants of Qesem were simply maximizing their local resources. In any case, this discovery adds an important new dimension to the knowhow, capabilities and perhaps taste preferences of these people.”

According to Prof. Gopher, the new evidence also raises possibilities concerning the division of labor at Qesem Cave. “Which part of the group found and collected the tortoises?” Prof. Gopher said. “Maybe members who were not otherwise involved in hunting large game, who could manage the low effort required to collect these reptiles — perhaps the elderly or children.”

“According to the marks, most of the turtles were roasted in the shell,” Prof. Barkai added. “In other cases, their shells were broken and then butchered using flint tools. The humans clearly used fire to roast the turtles. Of course they were focused on larger game, but they also used supplementary sources of food — tortoises — which were in the vicinity.”

The researchers are now examining bird bones that were recently discovered at Qesem Cave.

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Understanding how and why we evolved such large brains is one of the most puzzling issues in the study of human evolution. It is widely accepted that brain size increase is partly linked to changes in diet over the last 3 million years, and increases in meat consumption and the development of cooking have received particular attention from the scientific community. In a new study published in The Quarterly Review of Biology, Dr. Karen Hardy and her team bring together archaeological, anthropological, genetic, physiological and anatomical data to argue that carbohydrate consumption, particularly in the form of starch, was critical for the accelerated expansion of the human brain over the last million years, and coevolved both with copy number variation of the salivary amylase genes and controlled fire use for cooking.

With global increase in obesity and diet-related metabolic diseases, interest has intensified in ancestral or ‘Palaeolithic’ diets, not least because – to a first order of approximation – human physiology should be optimized for the nutritional profiles we have experienced during our evolution. Up until now, there has been a heavy focus on the role of animal protein and cooking in the development of the human brain over the last 2 million years, and the importance of carbohydrate, particular in form of starch-rich plant foods, has been largely overlooked.

Hardy’s team highlights the following observations to build a case for dietary carbohydrate being essential for the evolution of modern big-brained humans:

(1) The human brain uses up to 25% of the body’s energy budget and up to 60% of blood glucose. While synthesis of glucose from other sources is possible, it is not the most efficient way, and these high glucose demands are unlikely to have been met on a low carbohydrate diet;

(2) Human pregnancy and lactation place additional demands on the body’s glucose budget and low maternal blood glucose levels compromise the health of both the mother and her offspring;

(3) Starches would have been readily available to ancestral human populations in the form of tubers, as well as in seeds and some fruits and nuts;

(4) While raw starches are often only poorly digested in humans, when cooked they lose their crystalline structure and become far more easily digested;

(5) Salivary amylase genes are usually present in many copies (average ~6) in humans, but in only 2 copies in other primates. This increases the amount of salivary amylase produced and so increases the ability to digest starch. The exact date when salivary amylase genes multiplied remains uncertain, but genetic evidence suggests it was at some point in the last 1 million years.

Hardy proposes that after cooking became widespread, the co-evolution of cooking and higher copy number of the salivary amylase (and possibly pancreatic amylase) genes increased the availability of pre-formed dietary glucose to the brain and fetus, which in turn, permitted the acceleration in brain size increase which occurred from around 800,000 years ago onwards.

Eating meat may have kick-started the evolution of bigger brains, but cooked starchy foods together with more salivary amylase genes made us smarter still.